This application claims priority to German Patent Application No. DE 102 24 549.5, filed May 31, 2002, which is incorporated herein by reference in its entirety.
This invention relates to a steam iron having a steam chamber and a liquid reservoir.
In the case of a steam iron with a drip valve, water is introduced drop by drop from the water tank or liquid reservoir into a heated steam chamber. The steam generated in the steam chamber passes out of the sole plate through steam-outlet openings and comes into contact with the article which is to be ironed. The steam pressure in the steam chamber here usually corresponds merely to the atmospheric pressure or is increased by the value made up by the height of the water column in the water tank and the atmospheric pressure exerted thereon.
The steam-outlet openings are usually enclosed by a sole-plate surface, with the result that, in the case of particularly dense articles for ironing, such as denim, and/or an ironing board which is not particularly permeable to steam (e.g., made of wood), the steam pressure which can be generated by a steam iron with a drip valve is insufficient for discharging sufficient steam from the steam-outlet openings. In this case, on account of the articles for ironing not being particular permeable to steam, an elevated steam pressure builds up in the steam chamber, which is in pressure-equalizing connection with the steam outlet openings. The elevated steam pressure of the steam chamber is thus present on one side of the drip valve, said steam pressure opposing the atmospheric and water column pressure on the other side of the drip valve. The quantity of steam applied to the articles for ironing thus further decreases to a considerable extent.
In order to tackle this problem, it has been known for some time flow to connect the steam chamber to a liquid-free region of the water tank (the water tank is not completely filled) by means of a pressure-equalizing tube. By means of this solution, a steam pressure of the steam chamber, once elevated for example by the type of articles for ironing, no longer opposes the atmospheric pressure on the other side of the drip valve.
In practice, the hitherto used detailed solutions for a steam iron with pressure-equalizing device, although achieving an improved result, have not produced a sufficiently satisfactory result. In the case of portable steam irons according to DE 33 28 453, U.S. Pat. No. 2,387,281, U.S. Pat. No. 2,892,272 or GB 1,234,856, problems can arise if the water in the tank of the steam iron is moved back and forth by a normal ironing movement. As a result, for example, the steam directed into the water tank from the steam chamber is condensed on the tank wall by the water waves. With a water vapor to water volume ratio of approximately 1000 to 1, the condensation results in an undesirable drop in pressure and/or negative pressure in the water tank. The pressure fluctuations in the water tank which are generated by the wave movement of the water likewise have a disadvantageous effect on the pressure equilibrium between the steam chamber and water tank and on the pressure present at the drip valve.
It is thus an object of the present invention to provide a steam iron with pressure-equalizing device of the abovementioned type which eliminates the disadvantages of the prior art, which discharges a sufficient quantity of steam in particular even during movement of the steam iron and which manages without modifications which would result in higher production outlay in comparison with conventional technical solutions.
Various aspects of the invention feature a steam iron of the drip-valve type in which a pressure-equalizing device, such as a connecting tube, is arranged between a liquid reservoir and a steam chamber. The liquid reservoir and the liquid-filling region are preferably each not just liquid-tight, but also gas-tight, at least in a region of a pressure-equalizing passage between the liquid reservoir and steam chamber, such that it is possible to build up a gas pressure in the liquid reservoir. Provided in the region of the wall of the liquid reservoir of the liquid-filling region is a first one-way gas valve, through which ambient air can enter into the liquid reservoir.
Preferably, the first one-way gas valve opens automatically, such as in response to a certain threshold pressure value. It is preferable that the threshold pressure value be at or below atmospheric pressure. Accordingly, under negative gage pressure in the liquid reservoir, ambient air can be introduced into the liquid reservoir through the first one-way gas valve. The inherently disruptive wave movement of the water in the liquid reservoir, as described above, is thus advantageously exploited. The water moving back and forth in the liquid reservoir, usually to a pronounced extent as a result of the movement of the iron, functions effectively as a reciprocating pump or xe2x80x9cthermal pumpxe2x80x9d with the water acting as a moving piston. In the case of the water moving in the liquid reservoir, it is usually the case that one end region of the liquid reservoir is loaded with water to a considerably greater extent than an opposite region. A negative pressure is thus produced in the region of the liquid reservoir with the lower water content. A one-way gas valve arranged in a wall of the liquid reservoir in this negative-pressure region thus allows ambient air to enter, with the result that the movement of the water back and forth in the liquid reservoir leads to continuous replenishing with ambient air through the one-way gas valve.
In a further advantageous embodiment of the steam iron, a second one-way gas valve is provided on a wall of the liquid reservoir or of the liquid-filling region, the second valve allowing gas to pass out of the liquid reservoir in the opposite direction to the first one-way gas valve. This second one-way gas valve is preferably designed such that it opens automatically, such as in response to a positive threshold pressure value in the liquid reservoir, with the result that, in the case of a certain positive pressure in the liquid reservoir, gas is discharged from the liquid reservoir through the second one-way gas valve.
The threshold pressure value of the second one-way gas valve is preferably set at a positive gage pressure of greater than about 50 mbar (in some cases, greater than about 100 mbar), preferably at a level that does not occur during normal use of the steam iron. The second valve has a safety function in that it helps to avoid more extreme pressures in the liquid reservoir or steam chamber when the steam outlet openings are closed.
In some embodiments, the second one-way gas valve is designed as a closure of the liquid-filling region. The closure may latch into the housing or the wall of the liquid reservoir, for example, by means of a snap-in connection. The force which is necessary to release this snap-in connection is defined such that it corresponds to the positive threshold pressure value of the second one-way gas valve.
In some advantageous embodiments of the invention, there is no need for a second connection, requiring insulation and/or sealing, for the pressure-equalizing device between the liquid reservoir and steam chamber. For example, the drip valve may be provided with an inner tube, the cavity of which serves as a pressure-equalizing device.
According to one aspect of the invention, a steam iron has a sole plate with steam outlet openings in steam connection with a steam chamber, a heater that heats the sole plate and the steam chamber for the purpose of generating steam, and a liquid reservoir with a drip valve for supplying the steam chamber with liquid from the liquid reservoir. A pressure-equalizing passage extends between a first opening in the steam chamber and a second opening in a gas-tight region of the liquid reservoir. A first one-way gas valve is arranged between the liquid reservoir and ambient air to permit air to enter the liquid reservoir through the valve while impeding fluid flow from the liquid reservoir to the ambient air.
In some embodiments the one-way gas valve is arranged with respect to the liquid reservoir to cause air to enter the reservoir through the valve in response to motion of reservoir contents during motion of the iron during use. Preferably, the valve repetitively operates in response to normal reciprocating motion of the iron.
The one-way gas valve preferably opens automatically to permit air to enter the reservoir in response to pressure within the reservoir falling to below a predetermined threshold pressure. The predetermined threshold pressure is preferably less than or substantially equal to ambient atmospheric pressure.
In some cases, the drip valve is in the form of a channel defined between a movable rod and a wall separating the liquid reservoir and steam chamber. The rod may be operably connected to a knob exposed on the iron for manual manipulation by an operator, for example. In some embodiments, the rod also defines an internal cavity forming the pressure-equalizing passage between the liquid reservoir and steam chamber, advantageously reducing the number of holes necessarily formed in a lower wall of the reservoir.
The one-way gas valve is preferably located at one longitudinal end region of the liquid reservoir, Such as at a forward end.
In some embodiments, the iron has two such one-way gas valves arranged between the liquid reservoir and ambient air, the gas valves being disposed at opposite ends of the liquid reservoir.
In some instances, the gas valve is in the form of a ball check valve.
Some examples have a second one-way gas valve arranged between the liquid reservoir and ambient air, to permit air to leave the liquid reservoir through the valve. The second one-way gas valve preferably opens automatically to permit air to leave the reservoir in response to pressure within the reservoir rising to above a predetermined maximum threshold pressure. The predetermined maximum threshold pressure is preferably greater than normal reservoir operating pressure.
In some embodiments, the second one-way gas valve is manually openable for filling the liquid reservoir. In this way, the valve also serves as a closure of a liquid filling region.
Another aspect of the invention features a method of controlling, pressure in a liquid reservoir of a portable steam iron, incorporating many of the above-described features.
Another aspect of the invention features ironing clothes with the above-described steam iron.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.